1. Field of the Invention
This invention relates to energetic azido compounds and, more specifically, to a method for the synthesis of azido compounds under non-basic conditions, using acetyl azide as the azidation agent.
2. Description of the Prior Art
When 1,5-methylene-3,7-dinitro-1,3,5,7-tetrazacyclooctane (compound 1), a compound readily prepared by nitrolysis of hexamethylenetetramine, is treated with an equivalent of 98% nitric acid in excess acetic anhydride, 1-acetoxymethyl-3,5,7-trinitro-1,3,5,7-tetrazacyclooctane (compound 3) is formed. In the reaction, cleavage of the bridge occurs; one of the bridgehead nitrogen atoms acquires a nitro group, the other holds the acetoxymethyl group. The reaction may be considered to involve nitrolysis of (Compound 1) to the methyol derivative (Compound 2), followed by acetylation of the hydroxy group by the acetic anhydride. ##STR1## Bell and Dunstan (J.Chem.Soc.(c), 862-869 (1969)) investigated reactions of the six, seven, and eight-membered ring acetates with various nucleophiles such as alcohols and inorganic salts. One aspect of their work was the reactions of these ring acetates with sodium azide, in efforts to prepare the corresponding ring azides. The reaction of (Compound 3) and the six-membered ring acetate with sodium azide in dimethylformamide medium gave primarily decomposition products with a trace of (Compound 1). Only in the case of the seven-membered ring acetate was it possible to obtain the corresponding azido compound.
1-Azidomethyl-3,5,7-trinitro-1,3,5,7-tetracyclooctane (Compound 5) was of particular interest to our continuing studies on the synthesis of energetic azido compounds because of its structural relationship to the well-known high explosive 1,3,5,7-tetranitro-1,3,5,7-tetrazacyclooctane (HMX). Since Bell and Dunstan were unsuccessful in preparing (Compound 5) by the classical method of the treatment of (Compound 3) with sodium azide, other possible synthetic routes were investigated. It was apparent that under the basic conditions of the nucleophilic reaction with sodium azide, decomposition of the eight-membered ring was occurring. Therefore, the present invention concluded that the best chance for success with this reaction would be under nonbasic conditions.
Dunning and Dunning (J.Chem.Soc., 2925(1950)) have reported that treatment of 1-methoxymethyl-3,5-dinitro-1,3,5-triazacyclohexane with acetyl chloride and acetyl bromide gave 1-chloromethyl-3,5-dinitro-1,3,5-triazacyclohexane and 1-bromomethyl-3,5-dinitro-1,3,5-triazacyclohexane, respectively. This chemistry was applied to the current work on the eight-membered ring derivatives. Treatment of (Compound 3) with acetyl bromide gave a quatitative yield of 1-bromomethyl-3,5,7-trinitro-1,3,5,7-tetrazacyclooctane (Compound 4). Attempts to convert Compound 4 to Compound 5 with sodium azide were unsuccessful. Thus, a novel method Eq. 2 was needed and invented for the conversion of Compound 4 to Compound 5. ##STR2##